Morrison Bros. FMMASO Series Overfill Extended Body Warning Valve w/ Signal

Morrison Bros.
Extended Body Valve for use on double wall or vaulted tanks
2 in.
7.50 LBS
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The ASO series of valves is used to shut off the air supply to an AOD pump when the liquid level approaches full capacity.

The ATO valve is used to turn on the air supply to an AOD pump when the liquid level approaches the full capacity.


  • Installs directly into a 2” female threaded tank top opening
  • Accepts 1/4” air lines
  • When the ASO valve closes, the air supply is diverted to an audible whistle on the 91S and 91EXS models
  • Operating temperature range is -10ºF to 185ºF
  • Model ASO-91 and 91S shut off height is 7 inches from the tank top
  • Model ASO-91EX and 91EXS shut off height is 17?” inches from the tank top
  • Air flow capacity is 20 CFM @ 100 PSI
  • Maximum air pressure is 150 PSI
  • The valve will automatically reset as liquid is removed and the air pressure to the valve is turned off

Construction Details

  • Valve body and collar: Anodized aluminum
  • Float: Polypropylene
  • Float rod and valve spool: Brass
  • O-ring seals: Viton®
  • Hardware: Stainless and plated steel


  • ULC Listed
  • Florida DEP EQ 576
  • Patent 5007450 - Valve with optional alarm for use on used oil evacuation systems which use an air operated pump